Eugenol Inhibits the Biological Activities of an Oral Squamous Cell Carcinoma Cell Line SCC9 via Targeting MIF.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is a rampant cancer type in head and neck cancers with a poor prognosis and a high recurrence rate. Eugenol shows an anticancer effect in a variety of cancers, but it has been rarely studied in oral squamous cell carcinoma (OSCC). OBJECTIVE: The purpose of this study was to explore the role of Eugenol in OSCC and the underlying mechanism. METHODS: After different concentrations of Eugenol (0, 200, 400, and 800 µM) treatment, the viability, proliferation, migration, and invasion of OSCC cell line SCC9 were measured by CCK-8, colony formation, wound-healing, and transwell assays, respectively. TUNEL staining was employed to detect apoptosis. Western blotting was used to evaluate gene expression at the protein level. Molecular docking was used to identify the target of Eugenol. RESULTS: Eugenol decreased the proliferation and reduced the abilities of invasion and migration along with the expression of matrix metalloproteinases (MMP) 2 and MMP9 in SCC9 cells. On the contrary, the ratio of apoptotic cells was increased by Eugenol. In addition, Eugenol down-regulated B cell lymphoma-2 (Bcl-2) expression, but up-regulated BCL-2 associated X (Bax), cleaved caspase 3, and cleaved poly-ADP ribose polymerase (PARP) expression. Meanwhile, Eugenol exerted its effect on SCC9 cells in a concentration-dependent manner. Eugenol could bind to macrophage migration inhibitory factor (MIF), the expression of which was down-regulated after Eugenol treatment. Besides, overexpression of MIF reversed all the effects of Eugenol on OSCC cells. CONCLUSION: In summary, Eugenol suppressed the malignant processes of OSCC cells by targeting MIF, which could guide the clinical application of Eugenol in OSCC.

MIF inhibition as a strategy for overcoming resistance to immune checkpoint blockade therapy in melanoma.

Immune checkpoint blockade (ICB) has demonstrated an impressive outcome in patients with metastatic melanoma, yet, durable complete response; even with Ipilimumab/Nivolumab combo are under 30%. Primary and acquired resistance in response to ICB is commonly due to a tumor immune escape mechanism dictated by the tumor microenvironment (TME). Macrophage Migratory Inhibition Factor (MIF) has emerged as an immunosuppressive factor secreted in the TME. We have previously demonstrated that blockade of the MIF-CD74 signaling on macrophages and dendritic cells restored the anti-tumor immune response against melanoma. Here, we report that inhibition of the MIF-CD74 axis combined with ipilimumab could render resistant melanoma to better respond to anti-CTLA-4 treatment. We provide evidence that blocking the MIF-CD74 signaling potentiates CD8+ T-cells infiltration and drives pro-inflammatory M1 conversion of macrophages in the TME. Furthermore, MIF inhibition resulted in reprogramming the metabolic pathway by reducing lactate production, HIF-1α and PD-L1 expression in the resistant melanoma cells. Melanoma patient data extracted from the TCGA database supports the hypothesis that high MIF expression strongly correlates with poor response to ICB therapy. Our findings provide a rationale for combining anti-CTLA-4 with MIF inhibitors as a potential strategy to overcome resistance to ICB therapy in melanoma, turning a "cold" tumor into a "hot" one mediated by the activation of innate immunity and reprogramming of tumor metabolism and reduced PD-L1 expression in melanoma cells.

Wuchereria bancrofti macrophage migration inhibitory factor-2 (rWbaMIF-2) ameliorates experimental colitis.

Immunomodulatory molecules produced by helminth parasites are receiving much attention recently as novel therapeutic agents for inflammation and autoimmune diseases. In this study, we show that macrophage migration inhibitory factor (MIF) homologue from the filarial parasite, Wuchereria bancrofti (rWbaMIF-2), can suppress inflammation in a dextran sulphate sodium salt (DSS)-induced colitis model. The disease activity index (DAI) in DSS given mice showed loss of body weight and bloody diarrhoea. At autopsy, colon of these mice showed severe inflammation and reduced length. Administration of rWbaMIF-2 significantly reduced the DAI in DSS-induced colitis mice. rWbaMIF-2-treated mice had no blood in the stools, and their colon length was similar to the normal colon with minimal inflammation and histological changes. Pro-inflammatory cytokine genes (TNF-α, IL-6, IFN-γ, IL-1ß, IL-17A and NOS2) were downregulated in the colon tissue and peritoneal macrophages of rWbaMIF-2-treated mice. However, there were significant increases in IL-10-producing Treg and B1 cells in the colon and peritoneal cavity of rWbaMIF-2-treated mice. These findings suggested that rWbaMIF-2 treatment significantly ameliorated the clinical symptoms, inflammation and colon pathology in DSS given mice. This immunomodulatory effect of rWbaMIF-2 appeared to be by promoting the infiltration of Treg cells into the colon.

Therapeutic Potential of Hematopoietic Prostaglandin D2 Synthase in Allergic Inflammation.

Worldwide, there is a rise in the prevalence of allergic diseases, and novel efficient therapeutic approaches are still needed to alleviate disease burden. Prostaglandin D2 (PGD2) has emerged as a central inflammatory lipid mediator associated with increased migration, activation and survival of leukocytes in various allergy-associated disorders. In the periphery, the hematopoietic PGD synthase (hPGDS) acts downstream of the arachidonic acid/COX pathway catalysing the isomerisation of PGH2 to PGD2, which makes it an interesting target to treat allergic inflammation. Although much effort has been put into developing efficient hPGDS inhibitors, no compound has made it to the market yet, which indicates that more light needs to be shed on potential PGD2 sources and targets to determine which particular condition and patient will benefit most and thereby improve therapeutic efficacy. In this review, we want to revisit current knowledge about hPGDS function, expression in allergy-associated cell types and their contribution to PGD2 levels as well as beneficial effects of hPGDS inhibition in allergic asthma, rhinitis, atopic dermatitis, food allergy, gastrointestinal allergic disorders and anaphylaxis.

Macrophage migration inhibitory factor rescues mesenchymal stem cells from doxorubicin-induced senescence though the PI3K-Akt signaling pathway.

Doxorubicin (DOXO), an anthracycline antibiotic, is a commonly used anticancer drug. Despite its widespread usage, the therapeutic effects of DOXO are limited by its cardiotoxicity. Mesenchymal stem cell (MSC)-based therapies have had positive outcomes in the treatment of DOXO-induced cardiac damage; however, DOXO exerts toxic effects on MSCs, decreasing the effectiveness of MSC therapy. Macrophage migration inhibitory factor (MIF) promotes MSC survival and rejuvenation, and thus is a promising candidate to protect MSCs against DOXO-induced injury. The present study revealed that DOXO induced the senescence of MSCs, resulting in decreased proliferation, viability and paracrine effects. However, pretreatment with MIF improved the proliferation rate, viability, paracrine function, telomere length and telomerase activity of MSCs. Furthermore, the results indicated that the molecular mechanism underlying the anti-senescent function of MIF involved the phosphatidylinositol 3-kinase (PI3K)-RAC-α serine/threonine-protein kinase (Akt) signaling pathway, which MIF activated. In agreement with this finding, silencing Akt was identified to abolish the anti-senescent effect of MIF. In addition, MIF decreased oxidative stress in MSCs, as revealed by the decreased production of reactive oxygen species and malondialdehyde, and the increased activity of superoxide dismutase. These results indicate that MIF can rescue MSCs from a state of DOXO-induced senescence by inhibiting oxidative stress and activating the PI3K-Akt signaling pathway. Thus, treatment with MIF may have an important therapeutic application for the rejuvenation of MSCs in patients with cancer being treated with DOXO.

L-PGDS Mediates Vagus Nerve Stimulation-Induced Neuroprotection in a Rat Model of Ischemic Stroke by Suppressing the Apoptotic Response.

The role of lipocalin prostaglandin D2 synthase (L-PGDS) in brain ischemia has not been fully clarified to date. Vagus nerve stimulation (VNS) protects against cerebral ischemia/reperfusion (I/R) injury, but the mechanisms involved need further exploration. This study investigated the role of L-PGDS in cerebral I/R and whether this process was involved in the mechanism of VNS-mediated neuroprotection. Male Sprague-Dawley rats were pretreated with a lentiviral vector (LV) through intracerebroventricular injection, followed by middle cerebral artery occlusion (MCAO) and VNS treatment. The expression of L-PGDS in the peri-infarct cortex was examined. The localization of L-PGDS was determined using double immunofluorescence staining. Neurologic scores, infarct volume and neuronal apoptosis were evaluated at 24 h after reperfusion. The expression of apoptosis-related molecules was measured by western blot analysis. The expression of L-PGDS in the peri-infarct cortex increased at 12 h, reached a peak at 24 h after reperfusion, and lasted up to 3 days. VNS treatment further enhanced the expression of L-PGDS following ischemic stroke. L-PGDS was mainly expressed in neurons in the peri-infarct cortex. I/R rats treated with VNS showed better neurological deficit scores, reduced infarct volume, and decreased neuronal apoptosis as indicated by the decreased levels of Bax and cleaved caspase-3 as well as increased levels of Bcl-2. Strikingly, the beneficial effects of VNS were weakened after L-PGDS down-regulation. In general, our results suggest that L-PGDS is a potential mediator of VNS-induced neuroprotection against I/R injury.

Exogenous Administration of Recombinant MIF at Physiological Concentrations Failed to Attenuate Infarct Size in a Langendorff Perfused Isolated Mouse Heart Model.

PURPOSE: Evidence suggests a two-pronged role of endogenous macrophage migration inhibitory factor (MIF) release in ischemia/reperfusion injury. We aimed to assess whether its exogenous administration confers cardioprotection. METHODS: Male C57/BL6 mice were randomly allocated to receive recombinant mouse MIF (rMIF) at physiological (ng/mL) concentrations in a dose-response fashion before or after a protocol of 35 min of ischemia and 2 h of reperfusion in an isolated Langendorff-perfused model with infarct size as endpoint. Isolated primary cardiomyocytes were also used for cell survival studies using rMIF at a supra-physiological concentration of 1 µg/mL. Pro-survival kinase activation was also studied using Western blot analyses. RESULTS: Exogenous MIF did not elicit a cardioprotective effect either when administered before the ischemic insult or when applied at reperfusion. rMIF did not confer protection when it was applied immediately before or after a hypoxia/reoxygenation insult in primary isolated cardiomyocytes. Consistently, hearts treated with MIF did not show a significant increase in phosphorylated Akt and ERK1/2. CONCLUSION: The exogenous administration of rMIF in a physiological concentration range both before ischemia and at reperfusion did not show cardioprotective effects. Although these results do not address the role of endogenous MIF after an ischemic insult followed by reperfusion, they may limit the potential translational value of rMIF.

Potential role of aspirin in the prevention of aneurysmal subarachnoid hemorrhage.

BACKGROUND: Inflammation is a key element behind the pathophysiology of cerebral aneurysm formation and rupture. Aspirin is a potent inhibitor of cyclooxygenase-2 (COX), which plays a critical role in the expression of immune modulators known to contribute to cerebral aneurysm formation and rupture. Currently, there are no pharmacological therapies for patients with cerebral aneurysms. Both endovascular and microsurgical interventions may be associated with significant morbidity and mortality. Potentially, a medical alternative that prevents aneurysm progression and rupture may be a beneficial therapy for a significant number of patients. SUMMARY: In animal models, treatment with aspirin and genetic inactivation of COX-2 decreases aneurysm formation and rupture. Selective inhibition of COX-1 did not decrease aneurysm rupture, suggesting that selection inhibition of COX-2 may be critical in thwarting aneurysm progression. Walls of ruptured human intracranial aneurysms have higher levels of COX-2 and microsomal prostaglandin E2 synthase 1 (mPGES-1), both of which are known to be inhibited by aspirin. In a pilot study, patients undergoing microsurgical clipping had attenuated expression of COX-2, mPGES-1, and macrophages in aneurysm walls after 3 months of aspirin therapy versus those that did not receive aspirin. Additionally, in patients undergoing endovascular therapy, local circulating expression of chemokines and COX-2 were increased in blood samples taken from within aneurysm domes as compared to peripheral blood sample controls. Treatment with aspirin also resulted in decreased expression of COX-2 within leukocytes within aneurysms as compared to peripheral blood samples. Novel molecular imaging with ferumoxytol-enhanced MRI may help in the identification of patients at increased risk for aneurysm rupture and assessment of a response to aspirin therapy. Key Messages: Aspirin has been found to be a safe in patients harboring cerebral aneurysms and clinical studies provide evidence that it may decrease the overall rate of rupture. Furthermore, aspirin is an accessible and inexpensive medicine for patients who may not have access to endovascular or microsurgical treatment or for patients who are deemed low risk of aneurysm rupture, high risk for intervention, or both. Future clinical trials are indicated to determine the overall effect of aspirin on aneurysm progression and rupture. This review provides an update on the potential mechanisms and benefits of aspirin in the treatment of cerebral aneurysms.

Arzanol, a potent mPGES-1 inhibitor: novel anti-inflammatory agent.

Arzanol is a novel phloroglucinol α -pyrone, isolated from a Mediterranean plant Helichrysum italicum (Roth) Don ssp. microphyllum which belongs to the family Asteraceae. Arzanol has been reported to possess a variety of pharmacological activities. However, anti-inflammatory, anti-HIV, and antioxidant activities have been studied in some detail. Arzanol has been reported to inhibit inflammatory transcription factor NF κB activation, HIV replication in T cells, releases of IL-1 ß , IL-6, IL-8, and TNF-α , and biosynthesis of PGE2 by potentially inhibiting mPGES-1 enzyme. Diversity of mechanisms of actions of arzanol may be useful in treatment of disease involving these inflammatory mediators such as autoimmune diseases and cancer. This review presents comprehensive information on the chemistry, structure-activity relationship, and pharmacological activities of arzanol. In addition this review discusses recent developments and the scope for future research in these aspects.

Alphavirus replicon particles expressing TRP-2 provide potent therapeutic effect on melanoma through activation of humoral and cellular immunity.

BACKGROUND: Malignant melanoma is the deadliest form of skin cancer and is refractory to conventional chemotherapy and radiotherapy. Therefore alternative approaches to treat this disease, such as immunotherapy, are needed. Melanoma vaccine design has mainly focused on targeting CD8+ T cells. Activation of effector CD8+ T cells has been achieved in patients, but provided limited clinical benefit, due to immune-escape mechanisms established by advanced tumors. We have previously shown that alphavirus-based virus-like replicon particles (VRP) simultaneously activate strong cellular and humoral immunity against the weakly immunogenic melanoma differentiation antigen (MDA) tyrosinase. Here we further investigate the antitumor effect and the immune mechanisms of VRP encoding different MDAs. METHODOLOGY/PRINCIPAL FINDINGS: VRP encoding different MDAs were screened for their ability to prevent the growth of the B16 mouse transplantable melanoma. The immunologic mechanisms of efficacy were investigated for the most effective vaccine identified, focusing on CD8+ T cells and humoral responses. To this end, ex vivo immune assays and transgenic mice lacking specific immune effector functions were used. The studies identified a potent therapeutic VRP vaccine, encoding tyrosinase related protein 2 (TRP-2), which provided a durable anti-tumor effect. The efficacy of VRP-TRP2 relies on a novel immune mechanism of action requiring the activation of both IgG and CD8+ T cell effector responses, and depends on signaling through activating Fcγ receptors. CONCLUSIONS/SIGNIFICANCE: This study identifies a VRP-based vaccine able to elicit humoral immunity against TRP-2, which plays a role in melanoma immunotherapy and synergizes with tumor-specific CD8+ T cell responses. These findings will aid in the rational design of future immunotherapy clinical trials.

Mesenchymal stem cell-based gene therapy with prostacyclin synthase enhanced neovascularization in hindlimb ischemia.

OBJECTIVE: Bone marrow cell therapy contributes to collateral formation through the secretion of angiogenic factors by progenitor cells and muscle cells per se, thereby presenting a novel option for patients with critical limb ischemia. However, some cases are refractory to this therapy due to graft failure. Therefore, we used genetic modification of mesenchymal stem cells (MSCs) to overexpress a vasoregulatory protein, prostacyclin (PGI(2)), to examine whether it could enhance engraftment and neovascularization in hindlimb ischemia. METHODS AND RESULTS: We engineered the overexpression of PGI(2) synthase (PGIS) within MSCs, which resulted in higher expression levels of phosphorylated Akt and Bcl-2 than in control. Under hypoxic conditions, the overexpression of PGIS led to upregulated expression of cyclooxigenase-2 and peroxisome proliferator-activated receptor delta, following a 40% increased rate of proliferation in MSCs. We then produced unilateral hindlimb ischemia in C57BL6/J mice, which were injected either with MSCs transfected with GFP, with MSCs overexpressing PGIS, or with vehicle. Laser Doppler analyses demonstrated that the administration of MSCs effectively recovered blood perfusion, and that the peak blood flow was reached within 7 days of surgery in mice with MSCs overexpressing PGIS, which was earlier than that in mice with MSCs transfected with GFP. This beneficial effect was correlated to enhanced collateral formation and muscle bundle proliferation. CONCLUSION: Sustained release of PGI(2) enhanced the proangiogenic function of MSCs and subsequent muscle cell regrowth in the ischemic tissue suggesting potential therapeutic benefits of cell-based gene therapy for critical limb ischemia.

Combined triggering of dendritic cell receptors results in synergistic activation and potent cytotoxic immunity.

Elimination of malignant cells and intracellular infections involves collaboration between CTLs and Th1 inflammation. Dendritic cells drive this response via costimulation and cytokines. We have defined key signals required for the exponential expansion of specific CD8(+) T cells in vivo in mice. Immunization with two or more TLR agonists, anti-CD40, IFN-gamma, and surfactant were sufficient to drive unprecedented levels of CD8 response to peptide or protein Ag and highly polarized Th1 CD4 responses. CD40 signaling was required for CD8 expansion but could be provided by a concomitant CD4 Th response in place of anti-CD40. Triggering of these pathways activated migration and activation of myeloid and plasmacytoid dendritic cells and secretion of IL-12. Cross-presentation can thus be exploited to induce potent cytotoxic responses and long-term memory to peptide/protein Ags. When combined with a tumor-associated peptide from tyrosinase-related protein 2, our combined adjuvant approach effectively halted tumor growth in an in vivo melanoma model and was more effective than anti-CD40 and a single TLR agonist. Antitumor immunity was associated with long-lived effector memory CD8 cells specific for the naturally processed and presented tumor Ag, and tumor protection was partially but not entirely dependent on CD8 T cells. This flexible strategy is more effective than existing adjuvants and provides a technological platform for rapid vaccine development.

Novel C5a agonist-based dendritic cell vaccine in a murine model of melanoma.

A novel method to improve targeting and presentation of poorly immunogenic tumor-related antigens was investigated. This was performed with a molecular adjuvant constructed by covalently linking a response selective peptide agonist of C5a (YSFKDMP(MeL)aR) to known melanoma tumor-related antigens. C57Bl/6J mice were injected subcutaneously with bone marrow derived dendritic cells (DCs) pulsed with a melanoma epitope (TRP2-P2/Agonist), melanoma epitope tyrosinase (TYR/Agonist), a nonfunctional reverse conformation C5a agonist bound to TYR(reverse peptide) or DMSO-PBS vehicle. Mice were injected with the pulsed DCs and cytokines IL-2 and GMCSF three times prior to subcutaneous challenge with B16-F10 melanoma cells. All groups subsequently received DC vaccine boosters twice per week. Tumor growth was reduced and survival enhanced in mice immunized with the combination of TRP2-P2/Agonist and TYR/Agonist compared to mice receiving reverse peptide or vehicle.

A modified tyrosinase-related protein 2 epitope generates high-affinity tumor-specific T cells but does not mediate therapeutic efficacy in an intradermal tumor model.

The generation of tumor-specific T cells is hampered by the presentation of poorly immunogenic tumor-specific epitopes by the tumor. Here, we demonstrate that, although CD8+ T cells specific for the self/tumor Ag tyrosinase-related protein 2 (TRP2) are readily detected in tumor-bearing hosts, vaccination of either tumor-bearing or naive mice with an epitope derived from TRP2 fails to generate significant numbers of tetramer-staining TRP2-specific T cells or antitumor immunity. We identified an altered peptide epitope, called deltaV, which elicits T cell responses that are cross-reactive to the wild-type TRP2 epitope. Immunization with deltaV generates T cells with increased affinity for TRP2 compared with immunization with the wild-type TRP2 epitope, although TRP2 immunization often generates a greater number of TRP2-specific T cells based on intracellular IFN-gamma analysis. Despite generating higher affinity responses, deltaV immunization alone fails to provide any greater therapeutic efficacy against tumor growth than TRP2 immunization. This lack of tumor protection is most likely a result of both the deletion of high affinity and functional tolerance induction of lower affinity TRP2-specific T cells. Our data contribute to a growing literature demonstrating the ability of variant peptide epitopes to generate higher affinity T cell responses against tumor-specific Ags. However, consistent with most clinical data, simple generation of higher affinity T cells is insufficient to mediate tumor immunity.

Comparison of recombinant adenovirus and synthetic peptide for DC-based melanoma vaccination.

Optimal strategies for antigen-specific melanoma vaccination are currently being defined in experimental mouse models. Using a single H2-K(b)-binding peptide epitope derived from the melanosomal enzyme tyrosinase-related protein 2 (TRP2) in C57BL/6 mice, we show that adenovirus-transduced dendritic cells (DC) are clearly superior to peptide-pulsed DC for the induction of CD8+ T cells and antimelanoma immunity. Vaccine efficacy strictly depended on the presence of linked CD4+ T-cell help during the priming but not the effector phase of the immune response. These results provide important information for the translation of melanoma vaccine strategy in future clinical applications.

Targeting of antigens to activated dendritic cells in vivo cures metastatic melanoma in mice.

Anti (alpha)-DEC-205 antibodies target to the DEC-205 receptor that mediates antigen presentation to T cells by dendritic cells. To exploit these properties for immunization purposes, we conjugated the melanoma antigen tyrosinase-related protein (TRP)-2 to alphaDEC-205 antibodies and immunized mice with these conjugates together with dendritic cell-activating oligonucleotides (CpG). Upon injection of the melanoma cell line B16, alphaDEC-TRP immunized mice were protected against tumor growth. Even more important for clinical applications, we were able to substantially slow the growth of implanted B16 cells by injection of alphaDEC-TRP2 conjugates into tumor bearing hosts. Approximately 70% of the animals were cured from existing tumors by treatment with alphaDEC conjugates carrying two different melanoma antigens (TRP-2 and gp100). This protection was due to induction of melanoma-specific CD4 and CD8 responses. Thus, these data show that targeting of dendritic cells in situ by the means of antibody-antigen conjugates may be a novel way to induce long-lasting antitumor immunity.

Specific peptide-mediated immunity against established melanoma tumors with dendritic cells requires IL-2 and fetal calf serum-free cell culture.

Melanoma, despite its aggressive growth characteristics, is an antigenic tumor expressing several characterized neo- and differentiation antigens. Dendritic cells (DC) when pulsed with defined peptides have been shown to effectively induce melanoma-specific T cell responses in humans and mice. These protect animals from challenge with melanoma, but so far have failed to induce significant tumor regressions. To study the efficacy of DC-based anti-tumor vaccinations, we set up a therapeutic model using C57BL/6J mice with established pulmonary and subcutaneous metastases induced by the B16-melanoma cell line B78-D14. Mice were vaccinated twice with 20,000 antigen-presenting cells, either bone marrow-derived DC or epidermal Langerhans cells (LC), which were loaded with the tyrosinase-related protein 2 (TRP2) peptide. Generally, DC cultured with fetal calf serum (FCS) induced a dominant unspecific response. This was not seen using LC cultured without serum; however, vaccination with TRP2-loaded FCS-free LC alone failed to influence the growth of established B16 tumors. A reproducible reduction of tumor size and weight was only obtained if LC vaccinations with TRP2 were followed by a 5-day treatment of mice with 200,000 IU IL-2 intraperitoneally twice/daily. Omitting the TRP2 peptide abolished the efficacy of this combined treatment, demonstrating the crucial role of priming a melanoma-specific T cell response. Microcytotoxic assays performed with spleen-derived T cells and melanoma as well as congenic fibroblast lines as targets confirmed the TRP2-dependent specificity of LC-induced immune responses. Thus, despite the fact that tumor-specific T cells were primed, an additional IL-2-dependent stimulus was needed to translate this immune response into a therapeutic effect against established tumors.

Alternative roles for interferon-gamma in the immune response to DNA vaccines encoding related melanosomal antigens.

Tyrosinase-related proteins-1 and -2 (gp75/TRP-1 and TRP-2) are melanosomal membrane glycoproteins recognized by antibodies and T-cells from patients with melanoma. Xenogeneic DNA immunization against gp75/TRP-1 generates antibody-dependent tumor immunity and autoimmune depigmentation. In contrast xenogeneic TRP-2 DNA immunization induces immunity mediated by CD8+ T-cells. The role of IFN-gamma in the generation of tumor immunity and autoimmune depigmentation in these two models was investigated. No tumor protection and minimal depigmentation was observed after immunization with human TRP-2 DNA in mice deficient in IFN-gamma ligand. Repletion with recombinant murine IFN-gamma restored tumor immunity. Experiments using IL4 deficient mice demonstrated that tumor immunity was unaffected but that autoimmune depigmentation was potentially accelerated, consistent with down-modulation of autoimmunity against TRP-2 by IL4. In contrast, IFN-gamma was not required for the generation of immunity to gp75/TRP-1. In fact, exogenous IFN-gamma ablated autoantibody responses against gp75/TRP-1 after xenogeneic DNA immunization, consistent with a down-regulatory effect of IFN-gamma. These results show that immunity to TRP-2 following DNA immunization uses an IFN-gamma-dependent Th1 pathway, but immunity to gp75/TRP-1 is down-regulated by IFN-gamma.